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6p36s tube torture.

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nhuwar

nhuwar

Member
Joined 2007
I've got a few 6p36s tubes that I want to use in a push pull amp in the future. I don't really see now this tube has a max anode dissipation of 12 watts. The anode is almost the same as a 6550a. This is a heavy tube too so there's a fair amount of metal in there. So has anyone actually push one of these tubes to see what it can actually handle? I'm planning to use it triode wired.

The tube looks like it should be able to handle at least 30 watts of dissipation, but thats just a guess. I plan to test one but I haven't had the chance yet since there's other projects ahead of it.

I'd appreciate it if anyone could let me know what there experiences with this tube are.

Thanks,
Nick
 
smoking-amp

smoking-amp

Member
Joined 2001
I see some Ebayers are claiming 6P36S is the same as the EL500.

EL500: 12 Watt design center, 17 Watt design max, 280 deg. C max glass temp, Vg2=150 V knee at 500 mA

6P36S: 12 Watt max permissible, 17 Watt abs max (temp overload cond.), 230 deg. C max glass temp, Vg2=150 V knee at 400 mA

Looks more like 80% of an EL500.

Close, but not the same. Usually these TV sweep rated type tubes will allow an extra 35% Watts for audio rating and still 2000 Hr min. life. Beyond that, you probably need to figure the typical peak to avg. ratio for the signal being amplified. (compressed audio?) (Do the tubes have cooling radiators on the grid ends? Looks like EL500/6GB5 has cooling radiators)

If you have a 6JN6, 6GE5, or 6GV5 tube around, compare one to them, they're rated at 17 Watts design.
 
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smoking-amp

smoking-amp

Member
Joined 2001
You can get real XL500/13GB5 over here for $1:
Summer Dollar Days - Vacuum Tube Sale - $1.00 Vacuum Tubes

Takes magnoval sockets.

For triode configuration you can usually add the plate diss. rating + the screen diss. rating.
EL500 17 + 5 = 22 Watt
6P36S 12 + 5 = 17 W (datasheet says 16 Watt for triode)

Looks like $10 each with shipping for the 6P36S.

For $4 you could use a 6HJ5 and get a 24 + 6 = 30 Watt triode
For $11 you could use a 36LW6 and get a 40 + 7 = 47 Watt triode
Then there's GU50: 40 + 5 = 45 Watt triode
 
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Tubelab_com

Tubelab_com

Member
Joined 2005
tubelab.com
You can get real XL500/13GB5 over here for $1:
Click to expand...

Yeah, I bought 10 to play with. They were so much fun that I bought 150 more! The first 10 were Sylvania branded in new boxes. The next 150 were various brands, some in older and somewhat dirty boxes. Out of 160 tubes there were about 15 that were "Made in Korea". They looked rather wimpy but I didn't "test" one yet. The other 145 were ALL Mullards regardless of the brand on the tube.

Do they work? Well, I designed a rather unique circuit in LT Spice. It is a very complex two stage fully differential sweep tube amp that applied drive to both the screen grid, and the control grid of the output tubes. Local feedback was used around the driver and output stage. The simulation predicted a power VS distortion curve that yielded about 100 watts at 1% distortion and 5% distortion at 140 watts. It predicted a plate efficiency at full power of 80%. I breadboarded the amp and tested it. The performance wasn't too far from the simulated predictions. At 100 watts the distortion was about 1.5% and power at clip was 150 watts! Running the amp at this level for 5 minutes produced a pale glow from the plates. 100 watts for half an hour made my load resistors very hot, but all else remained cool.


For $4 you could use a 6HJ5 and get a 24 + 6 = 30 Watt triode
Click to expand...

Haven't tried triode, but 125 WPC is no problem in pentode. Tested in Petes "engineers amp". At least 10 people built this 125 WPC version.

For $11 you could use a 36LW6 and get a 40 + 7 = 47 Watt triode
Click to expand...

I like the 'LW6 tube a lot. There at least 5 different constructions in 2 different bottle sizes. The wimpiest 36LW6 with no heat radiating fins in the skinny bottle will dissipate 50 watts all day long without issue. The fat bottled 6LW6 with big heat radiating fins will run forever at 75 watts, and doesn't show even a hint of plate color until 90 watts. I have extracted 250 watts from a pair of these in pentode with no issue, and this was a guitar amp running 750 volts on the plate! I have used these in triode too, but my big SE triode amp ended up scrapped after the fourth random tube failure. The amp played beautifully for weeks, even months, then zap, a tube would just run away. Granted I ran the big fat boys on 400 volts at 100 mA in triode. So, if you are tempted to go there, I would stick to 350 volts or less.
 
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